The general objectives of the project are the same as previously listed. To elucidate the gross comformation of DNA in isolated condensed chromosomes and to define the molecular interactions which organize and stabilize the condensed state of this structure. More specifically, we intend to 1) define interactions which stabilize DNA folds in isolated bacterial nucleoids and in condensed chromatin isolated from interphase nuclei of Drosophila cells, 2) define interactions segregating the DNA into separate domains of supercoiling in the isolated chromosomes, 3) determine if the condensed DNA is a static or dynamic structure, 4) investigate the state of supercoiling of DNA and its segregation in the isolated condensed chromatin from Drosophila cells. BIBLIOGRAPHICAL REFERENCES: Giorno, R., R. Hecht, and D. Pettijohn, "Analysis by Isopyonic Centrifugation of Isolated Nucleoids of Escherichia coli," Nucleic Acids Research 2, 1159-1567(1975). Hecht, R. and D. Pettijohn, "RNA Molecules Attached to DNA in Isolated Bacterial Nucleoids: their Possible Role in Stablilizing the Condensed Chromosome." in DNA Synthesis and Its Regulation, eds. Goulian, Hanawalt and Fox, Benjamin, Inc., (in press).